The present invention relates to actuators for disc brake calipers, and it more particularly pertains to a system for manually releasing spring applied brake applications.
In the prior Engle U.S. Pat. No. 4,018,140, an actuator for disc brakes is disclosed having spring applied emergency brakes wherein Belleville springs are normally compressed by fluid in a chamber on one side of an emergency piston. Upon release of fluid from the chamber, disc brakes are applied by spring actuated movement of the emergency piston. Provision is made for hand operated release of the emergency brake application in case of loss of availability of fluid pressure to release the brakes. This is accomplished by threading a retraction screw into the emergency piston to cause the Belleville springs to be compressed mechanically to the same extent as by fluid pressure operation of the piston.
In a typical example of manual release of a spring brake application in the system according to the above patent, manually exerted force in rotating the retraction screw is large because of the spring load to be overcome, which is approximately 11,500 lbs.
An object of the present invention is to provide an improved system for manually releasing spring applied brake applications which substantially obviates one or more of the limitations and disadvantages of the described prior art systems.
Another object of the present invention is to materially reduce the force required to manually release a spring disc brake application.
Other objects, purposes and characteristic features of the present invention will be in part obvious from the accompanying drawings, and in part pointed out as the description of the invention progresses.